U.S. patent application number 15/692266 was filed with the patent office on 2018-06-14 for method for producing lithium phosphate from a lithium solution.
This patent application is currently assigned to SUNGEEL HITECH CO., LTD.. The applicant listed for this patent is SUNGEEL HITECH CO., LTD.. Invention is credited to Suk-Hyun BYUN, Woo-Young JUNG, Kwang-Joong KIM, Ki-Woong LEE, Kang-Myung YI.
Application Number | 20180166753 15/692266 |
Document ID | / |
Family ID | 59357230 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180166753 |
Kind Code |
A1 |
BYUN; Suk-Hyun ; et
al. |
June 14, 2018 |
METHOD FOR PRODUCING LITHIUM PHOSPHATE FROM A LITHIUM SOLUTION
Abstract
An embodiment of the present invention provides a method for
producing lithium phosphate from a lithium solution, comprising the
steps of, preparing a mixture in which a phosphorus-containing
material is added to a lithium solution in step 1; adding a basic
solution to the prepared mixture to adjust the pH to 10 to 12 in
step 2; and making the pH-adjusted mixture react by raising its
temperature and filtering to recover lithium phosphate in step
3.
Inventors: |
BYUN; Suk-Hyun;
(Jeollabuk-do, KR) ; YI; Kang-Myung; (Seoul,
KR) ; LEE; Ki-Woong; (Gyeonggi-do, KR) ; KIM;
Kwang-Joong; (Jeollabuk-do, KR) ; JUNG;
Woo-Young; (Jeollabuk-do, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUNGEEL HITECH CO., LTD. |
Jeollabuk-do |
|
KR |
|
|
Assignee: |
SUNGEEL HITECH CO., LTD.
Jeollabuk-do
KR
|
Family ID: |
59357230 |
Appl. No.: |
15/692266 |
Filed: |
August 31, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02W 30/84 20150501;
C01D 15/08 20130101; C01D 15/00 20130101; C01B 25/306 20130101;
H01M 10/54 20130101; C22B 7/008 20130101 |
International
Class: |
H01M 10/54 20060101
H01M010/54; C01D 15/00 20060101 C01D015/00; C22B 7/00 20060101
C22B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2016 |
KR |
10-2016-0170421 |
Claims
1. A method for producing lithium phosphate from a lithium
solution, comprising the steps of, preparing a mixture in which a
phosphorus-containing material is added to a lithium solution in
step 1; adding a basic solution to the prepared mixture to adjust
the pH to 10 to 12 in step 2; and making the pH-adjusted mixture
react by raising its temperature and filtering to recover lithium
phosphate in step 3.
2. A method of claim 1, wherein the lithium solution of step 1 is a
waste solution of a waste lithium battery.
3. A method of claim 1, wherein the lithium concentration of the
lithium solution of step 1 is 1.5 g/L to 6.0 g/L.
4. A method of claim 1, wherein the phosphorus-containing material
of step 1 comprises phosphoric acid (H.sub.3PO.sub.4) or
phosphate.
5. A method of claim 1, wherein the phosphorus-containing material
addition ratio of step 1 is 0.8 to 1.2 times a lithium equivalent
of the lithium solution.
6. A method of claim 1, wherein the basic solution of step 2 is a
basic solution comprising one or more selected from a group
consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH),
magnesium hydroxide (Mg(OH).sub.2) and calcium hydroxide
(Ca(OH).sub.2).
7. A method of claim 1, wherein the addition of the basic solution
of step 2 is performed such that the pH of the mixture is 10.5 to
11.5.
8. A method of claim 1, wherein the temperature rise in step 3 is
performed by raising the temperature to 70.degree. C. to 90.degree.
C. and a reaction is made by maintaining the temperature for 30
minutes to 90 minutes after raising the temperature.
9. A method of claim 1, wherein the filtration of step 3 recovers
lithium phosphate containing 85 wt % to 98 wt % of lithium with
respect to lithium in the lithium solution of step 1.
10. A method for producing lithium phosphate from a lithium
solution, comprising the steps of, preparing a mixture in which
phosphoric acid is added to a lithium solution in step i; adding a
basic solution to the prepared mixture to adjust the pH to 10 to 12
in step ii; and making the pH-adjusted mixture react by raising its
temperature to 70.degree. C. to 90.degree. C. and filtering to
recover lithium phosphate in step iii.
11. A method for producing lithium phosphate from a waste solution
from a waste battery containing lithium, comprising the steps of,
preparing a mixture in which phosphoric acid is added 0.8 to 1.2
times the lithium equivalent of a waste solution of a waste lithium
battery containing lithium at a concentration of 1.5 g/L to 6.0
g/L, to the waste solution in step a; adding sodium hydroxide to
the prepared mixture to adjust the pH to 10 to 12 in step b; and
raising the temperature of the pH-adjusted mixture to 70.degree. C.
to 90.degree. C. and making it react for 30 to 90 minutes and
filtering to recover lithium phosphate containing 85 wt % to 98 wt
% of lithium with respect to lithium in the waste solution of step
a in step c.
12. Lithium phosphate produced through the method of claim 1,
wherein the lithium phosphate comprises 85 wt % to 98 wt % of
lithium with respect to the lithium content in the lithium waste
solution which is a starting material at the time of the
production.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent
Application No. 10-2016-0170421 filed on Dec. 14, 2016, and all the
benefits accruing therefrom under 35 U.S.C. .sctn. 119, the content
of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to method for producing
lithium phosphate from a lithium solution.
Description of the Related Art
[0003] Recently, attention has been focused on a method for
recovering expensive lithium compounds. As a widely known method
for recovering a lithium compound, there is a method of dissolving
a positive electrode material of a waste lithium secondary battery
using a strong acid such as nitric acid, sulfuric acid,
hydrochloric acid, and the like, and then performing a
neutralization reaction to separate and recover lithium and other
metal compounds (Korean Laid-Open Patent Publication No.
10-2014-0126943). However, the above-described recovery method
requires expensive chemicals and additional processes must be
performed to solve the environmental problems caused by the use of
acid, which is pointed out as a problem in that it is not
economical.
SUMMARY OF THE INVENTION
[0004] Accordingly, the present invention has been made keeping in
mind the above problems occurring in the prior art, and an object
of the present invention is to provide a method for producing
lithium phosphate which is economical, environmentally friendly,
and exhibits a high lithium recovery rate by recovering, lithium
phosphate by adding a phosphorus-containing, material to a lithium
solution.
[0005] In order to achieve the above object, according to one
aspect of the present invention, a method for producing lithium
phosphate from a lithium solution is provided, including the steps
of, preparing a mixture in which a phosphorus-containing material
is added to a lithium solution in step 1; adding a basic solution
to the prepared mixture to adjust the pH to 10 to 12 in step 2; and
making the pH-adjusted mixture react by raising its temperature and
filtering to recover lithium phosphate in step 3.
[0006] In one embodiment, the lithium solution of step 1 may be a
waste solution of a waste lithium battery.
[0007] In one embodiment, the lithium concentration of the lithium
solution of step 1 may be from 1.5 g/L to 6.0 g/L.
[0008] In one embodiment, the phosphorus-containing material of
step 1 may comprise phosphoric acid (H.sub.3PO.sub.4) or
phosphate.
[0009] In one embodiment, the phosphorus-containing material
addition ratio of step 1 may be 0.8 to 1.2 times the lithium
equivalent of the lithium solution.
[0010] In one embodiment, the basic solution of step 2 is a basic
solution including one or more selected from a group consisting of
sodium hydroxide (NaOH), potassium hydroxide (KOH), magnesium
hydroxide (Mg(OH).sub.2) and calcium hydroxide (Ca(OH).sub.2).
[0011] In one embodiment, the addition of the basic solution of
step 2 may be performed such that the pH of the mixture is from
10.5 to 11.5.
[0012] In one embodiment, the temperature rise in step 3 may be
performed by raising the temperature to 70.degree. C. to 90.degree.
C. and may be made to react by maintaining the temperature for 30
minutes to 90 minutes alter raising the temperature.
[0013] In one embodiment, the filtration of step 3 may recover
lithium phosphate containing 85 wt % to 98 wt % of lithium with
respect to lithium in the lithium solution of step 1.
[0014] According to another aspect of the present invention, a
method for producing lithium phosphate from a lithium solution is
provided, including the steps of, preparing a mixture in which
phosphoric acid is added to a lithium solution in step i; adding a
basic solution to the prepared mixture to adjust the pH to 10 to 12
in step ii; and making the pH-adjusted mixture react by raising its
temperature to 70.degree. C. to 00.degree. C. and filtering to
recover lithium phosphate in step iii.
[0015] Further, in order to achieve the above object, according to
another aspect of the present invention, a method for producing
lithium phosphate from a waste solution from a waste battery
containing lithium is provided, including the steps of, preparing a
mixture in which phosphoric acid is added 0.8 to 1.2 times the
lithium equivalent of a waste solution of a waste lithium battery
containing lithium at a concentration of 1.5 g/L to 6.0 g/L, to the
waste solution in step a; adding sodium hydroxide to the prepared
mixture to adjust the pH to 10 to 12 in step b; and raising the
temperature of the pH-adjusted mixture to 70.degree. C. to
90.degree. C. and making it react for 30 to 90 minutes and
filtering to recover lithium phosphate containing 85 wt % to 98 wt
% of lithium with respect to lithium in the waste solution of step
a in step c.
[0016] Further, in order to achieve the above object, according to
another aspect of the present invention, lithium phosphate produced
through any one of the above-mentioned methods is provided, wherein
the lithium phosphate comprises 85 wt % to 98 wt % of lithium with
respect to the lithium content in the lithium waste solution which
is a starting material at the time of the production.
[0017] According to an aspect of the present invention, lithium
phosphate containing 85 wt % to 98 wt % of lithium with respect to
lithium in the lithium solution can be recovered.
[0018] It should be understood that the effects of the present
invention are not limited to the above effects and include all
effects that can be deduced from the detailed description of the
present invention or the configuration of the invention described
in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a flowchart showing an example of a method for
producing lithium phosphate from a lithium solution according to an
embodiment of the present invention.
[0020] FIG. 2 is a flowchart showing the method for producing
lithium phosphate, the lithium-based weight ratio of each step, and
the total weight ratio of Example 1 of the present invention.
[0021] FIG. 3 is a graph showing the lithium content of lithium
phosphate with respect to waste solution lithium by pH adjustment
of the present invention.
[0022] FIG. 4 is a graph showing the lithium content of lithium
phosphate with respect to the waste solution lithium through
temperature-raising temperature control of the present
invention.
[0023] FIG. 5 is a graph showing the lithium concentration of the
filtrate after recovering lithium phosphate through pH adjustment
of the present invention.
[0024] FIG. 6 is a graph showing the relative comparison of the
amounts of sodium hydroxide (NaOH) used in the pH adjustment of the
present invention with pH 11 being the standard.
[0025] FIG. 7 is a graph showing the lithium concentration of the
filtrate after recovering lithium phosphate through
temperature-raising temperature control.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Exemplary embodiments of the present disclosure will be
described in detail below with reference to the accompanying
drawings.
[0027] The advantages and/or features of the present invention and
the manner of achieving them will become apparent by referring to
various embodiments described in detail below with reference to the
accompanying drawings.
[0028] However, the present invention is not limited to the
configurations of the embodiments described below, but may be
embodied in various other forms, and each embodiment disclosed in
this specification is intended to be illustrative only, and it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the invention as defined by the
appended claims.
[0029] Also, in the following description of the present invention,
a detailed description of a configuration that is considered to
unnecessarily obscure the gist of the present invention, for
example, a known technology including the prior art, may be
omitted.
[0030] According to an aspect of the present invention, a method
for producing lithium phosphate from a lithium solution is
provided, including the steps of, [0031] preparing a mixture in
which a phosphorus-containing material is added to a lithium
solution in step 1 in S10; [0032] adding a basic solution to the
prepared mixture to adjust the pH to 10 to 12 in step 2 in S20; and
[0033] making the pH-adjusted mixture react by raising its
temperature and filtering to recover lithium phosphate in step 3 in
S30.
[0034] Hereinafter, an example of a method for producing lithium
phosphate from a lithium solution according to one aspect of the
present invention will be described in detail for each step.
[0035] In the method for producing lithium phosphate from a lithium
solution according to an aspect of the present invention, a mixture
where a phosphorus-containing material is added to a lithium
solution is prepared in step 1 in S10.
[0036] The lithium solution of step 1 may be a waste solution of a
waste lithium battery.
[0037] The lithium concentration of the lithium solution of step 1
may be from 1.5 g/L to 6.0 g/L, and preferably from 1.5 g/L to 3.5
g/L. If the lithium concentration is less than 1.5 g/L, the lithium
recovery rate may decrease in the filtration step described later.
If the lithium concentration is more than 6.0 g/L, it may be
economical to recover lithium carbonate by evaporation
concentration.
[0038] The phosphorus-containing material of step 1 may comprise
phosphoric acid (H.sub.3PO.sub.3) or phosphate, and the phosphate
may be one or more selected from a group consisting of potassium
phosphate, sodium phosphate, aluminum phosphate, zinc phosphate,
ammonium polyphosphate and sodium hexametaphosphate and the like,
and preferably a phosphorus-containing material containing
phosphoric acid can be used.
[0039] The addition ratio of the phosphorus-containing material in
step 1 may be 0.8 to 1.2 times, preferably 0.9 to 1.1 times, the
lithium equivalent of the lithium solution. If the
phosphorus-containing material is added in an equivalent amount
less than 0.8 times the lithium of the lithium solution, the
recovery rate of lithium may be lowered in the filtration step to
be described later. If the phosphorus-containing material is added
in an equivalent amount more than 1.2 times the lithium of the
lithium solution, the use of excessive phosphorus-containing
material can result in economic waste and increased wastewater
treatment costs.
[0040] In the method for producing lithium phosphate from the
lithium solution according to one aspect of the present invention,
a basic solution is added to the prepared mixture to adjust the pH
to 10 to 12 in step 2 in S20.
[0041] The basic solution of step 2 is a basic solution including
one or more selected from a group consisting of sodium hydroxide
(NaOH), potassium hydroxide (KOH), magnesium hydroxide
(Mg(OH).sub.2) and calcium hydroxide (Ca(OH).sub.2).
[0042] The basic solution of step 2 may be added so that the pH of
the mixture is 10 to 12, preferably 10.5 to 11.5. If the pH of the
mixture is less than 10, a problem may occur where the recovery
rate is lowered. If the pH of the mixture is more than 12, first, a
side effect of decrease in recovery rate may occur. This may result
in the formation of a very small amount of lithium hydroxide due to
the addition of a large amount of sodium hydroxide and may result
in an increase in the Li concentration in the lithium recovery
filtrate due to the solubility of the formed lithium hydroxide.
Next, the amount of sodium hydroxide used to raise the pH to 12 or
higher is, 5.25 times as much for pH 13 and 10 times as much for pH
13.5, as that of pH 11, and so the process cost may increase due to
the increase in the amount of drug being used, and also, there is a
problem of increase in wastewater treatment costs due to excessive
use of sodium hydroxide and an increase in waste disposal costs due
to increase of process sludge.
[0043] In the method for producing lithium phosphate from the
lithium solution according to one aspect of the present invention,
the temperature of the pH-adjusted mixture is raised to make it
react and filtered to recover lithium phosphate in step 3 in
S30.
[0044] The temperature rise in step 3 may be performed by raising
the temperature to 70.degree. C. to 90.degree. C. and may be made
to react by maintaining the temperature for 30 minutes to 90
minutes after raising the temperature. At this time, the lithium
phosphate solid component can be easily produced by the
reaction.
[0045] The filtration in step 3 above can recover the solid lithium
phosphate produced in the reaction and the remaining filtrate can
be treated as wastewater.
[0046] The filtration of step 3 may recover lithium phosphate
containing 85 wt % to 98 wt % of lithium with respect to lithium in
the lithium solution of step 1, and preferably lithium phosphate
containing 95 wt % to 98 wt % of lithium with respect to lithium in
the lithium solution of step 1, can recovered.
[0047] Step 3 may further include washing the lithium phosphate
recovered by the filtration.
[0048] The lithium phosphate produced by the above-described method
(steps 1 to 3, S10 to S30) can be used as a raw material in a
process for producing lithium carbonate.
[0049] The method for producing lithium phosphate from the lithium
solution according to one aspect of the present invention may not
include the step of removing organic matter that may remain in the
lithium solution.
[0050] According to another aspect of the present invention, a
method for producing lithium phosphate from a lithium solution is
provided, including the steps of,
[0051] preparing a mixture in which phosphoric acid is added to a
lithium solution in step i;
[0052] adding a basic solution to the prepared mixture to adjust
the pH to 10 to 12 in step ii; and
[0053] making the pH-adjusted mixture react by raising its
temperature to 70.degree. C. to 90.degree. C. and filtering to
recover lithium phosphate in step iii.
[0054] In the method for producing lithium phosphate from the
lithium solution according to one aspect of the present invention,
step i produces a mixture in which phosphoric acid is added to
lithium solution.
[0055] The lithium concentration of the lithium solution of step i
may be the same as the lithium concentration of the lithium
solution of step 1 above.
[0056] The lithium solution of step i may be a waste solution of a
waste lithium battery.
[0057] The added amount of the phosphoric acid in step i may be the
same as the added amount of the phosphorus-containing material in
step 1.
[0058] In the method for producing lithium phosphate from the
lithium solution according to one aspect of the present invention,
step ii is a step of adjusting the pH to 10 to 12 by adding a basic
solution to the prepared mixture.
[0059] The basic solution of step ii may be the same as the basic
solution of step 2 above.
[0060] The basic solution of step ii may be added so that the pH of
the mixture becomes 10 to 12, preferably 10.5 to 11.5. If the pH of
the mixture is less than 10, there may be a problem that the
recovery rate is lowered. If the pH of the mixture is more than 12,
first a side effect of decrease in recovery rate may occur. This
may result in the formation of a very small amount of lithium
hydroxide due to the addition of a large amount of sodium hydroxide
and may result in an increase in the Li concentration in the
lithium recovery filtrate due to the solubility of the formed
lithium hydroxide. Next, the amount of sodium hydroxide used to
raise the pH to 12 or higher is, 5.25 times as much for pH 13 and
10 times as much for pH 13.5, as that of pH 11, and so the process
cost may increase due to the increase in the amount of drug being
used, and also, there is a problem of increase in wastewater
treatment costs due to excessive use of sodium hydroxide and an
increase in waste disposal costs due to increase of process
sludge.
[0061] In the method for producing lithium phosphate from a lithium
solution according to one aspect of the present invention, the
pH-adjusted mixture is made to react by raising its temperature to
70.degree. C. to 90.degree. C. and filtering to recover lithium
phosphate in step iii.
[0062] The reaction time at the time of raising the temperature in
step iii may be the same as the step 3.
[0063] The filtration in step iii can recover the lithium phosphate
as in step 3 and treat the remaining filtrate as wastewater.
[0064] The lithium content of the lithium phosphate recovered in
step iii may be the same as the content of step 3.
[0065] Step iii may further include washing the recovered lithium
phosphate as in step 3.
[0066] The lithium phosphate produced by the above method can be
used as a raw material in a process for producing lithium
carbonate.
[0067] According to another aspect of the present invention, a
method for producing lithium phosphate from a waste solution from a
waste battery containing lithium is provided, including the steps
of,
[0068] preparing a mixture in which phosphoric acid is added 0.8 to
1.2 times the lithium equivalent of a waste solution of a waste
lithium battery containing lithium at a concentration of 1.5 g/L to
6.0 g/L, to the waste solution in step a;
[0069] adding sodium hydroxide to the prepared mixture to adjust
the pH to 10 to 12 in step b; and
[0070] raising the temperature of the pH-adjusted mixture to
70.degree. C. to 90.degree. C. and making it react for 30 to 90
minutes and filtering to recover lithium phosphate containing 85 wt
% to 98 wt % of lithium with respect to lithium in the waste
solution of step a in step c.
[0071] The basic solution of step b may be added so that the pH of
the mixture becomes 10 to 12, preferably 10.5 to 11.5. If the pH of
the mixture is less than 10, there may be a problem that the
recovery rate is lowered. If the pH of the mixture is more than 12,
first, a side effect of decrease in recovery rate may occur. This
may result in the formation of a very small amount of lithium
hydroxide due to the addition of a large amount of sodium hydroxide
and may result in an increase in the Li concentration in the
lithium recovery filtrate due to the solubility of the formed
lithium hydroxide. Next, the amount of sodium hydroxide used to
raise the pH to 12 or higher is, 5.25 times as much for pH 13 and
10 times as much for pH 13.5, as that of pH 11, and so the process
cost may increase due to the increase in the amount of thug being
used, and also, there is a problem of increase in wastewater
treatment costs due to excessive use of sodium hydroxide and an
increase in waste disposal costs due to increase of process
sludge.
[0072] In the filtration of step c, lithium phosphate may be
recovered as in step 3 and the remaining filtrate may be subject to
wastewater treatment.
[0073] Step c may further include washing the recovered lithium
phosphate as in the step 3.
[0074] The lithium phosphate produced by the above method can be
used as a raw material in a process for producing lithium
carbonate.
[0075] According to another aspect of the present invention,
[0076] a lithium phosphate produced by any one of the
above-mentioned methods for producing lithium phosphate is
provided.
[0077] The produced lithium phosphate may be lithium phosphate
comprising 85 wt % to 98 wt % of lithium with respect to the
lithium content in the lithium waste solution which is a starting
material at the time of the production.
[0078] Hereinafter, the present invention will be described in more
detail with reference to examples and experimental examples.
However, the following examples and experimental examples are for
illustrative purposes only and are not intended to limit the scope
of the present invention.
<Example 1> Production Process of Lithium Phosphate
[0079] Step 1: 10 tons of a lithium waste solution (lithium
concentration: 3 g/L) of a waste lithium secondary battery was
provided. Phosphoric acid was added to the waste solution at a
molar equivalent (180 kg) with respect to the lithium.
[0080] Step 2: 720 kg of sodium hydroxide (20% concentrations) was
added to the phosphoric acid-added waste solution to adjust the pH
to 11.
[0081] Step 3: The temperature of the pH-adjusted waste solution
was raised to a temperature of 80.degree. C., made to react for 1
hour, and then filtered to collect lithium phosphate, which was
washed with distilled water.
<Example 2> Production Process of Lithium Phosphate, pH
10
[0082] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 10.
<Example 3> Production Process of Lithium Phosphate, pH
12
[0083] Lithium Phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 12.
<Comparative Example 1> Production Process of Lithium
Phosphate, pH 9
[0084] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 9.
<Comparative Example 2> Production Process of Lithium
Phosphate, pH 13
[0085] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 13.
<Comparative Example 3> Production Process of Lithium
Phosphate, pH 13.5
[0086] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 13.5.
<Example 4> Production Process of Lithium Phosphate,
70.degree. C.
[0087] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 3 of Example 1, the temperature was
raised to 70.degree. C.
<Example 5> Production Process of Lithium Phosphate,
90.degree. C.
[0088] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 3 of Example 1, the temperature was
raised to 90.degree. C.
<Comparative Example 4> Production Process of Lithium
Phosphate, 50.degree. C.
[0089] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 3 of Example 1, the temperature was
raised to 50.degree. C.
<Comparative Example 5> Production Process of Lithium
Phosphate, 100.degree. C.
[0090] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 3 of Example 1, the temperature was
raised to 100.degree. C.
<Comparative Example 6> Production Process of Lithium
Phosphate, pH 8
[0091] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 8.
<Comparative Example 7> Production Process of Lithium
Phosphate, pH 7
[0092] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 2 of Example 1, the pH was adjusted
to 7.
<Comparative Example 8> Production Process of Lithium
Phosphate, 60.degree. C.
[0093] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 3 of Example 1, the temperature was
raised to 60.degree. C.
<Comparative Example 9> Production Process of Lithium
Phosphate, 25.degree. C.
[0094] Lithium phosphate was produced in the same manner as in
Example 1, except that in step 3 of Example 1, the temperature was
raised to 2555.degree. C.
<Experimental Example 1> Comparison of the Recovery Rate of
Lithium According to pH Adjustment
[0095] The lithium content according to the pH adjustment of the
lithium phosphate produced in Examples 1 to 3 and Comparative
Examples 1 to 3, 6 and 7 was compared based on the lithium content
of the initial waste solution and a relative value of the amount of
sodium hydroxide (NaOH) used was compared, and the results are
shown in Table 1 and FIG. 3 below.
TABLE-US-00001 TABLE 1 Lithium content of lithium phosphate Used
amount of Concentration with respect sodium hydroxide of filtrate
after to waste pH of (relative comparison Li recovery solution step
1 compared to pH 11) (ppm) lithium Example 1 11 1.00 169 95 wt %
Example 2 10 0.81 441 87 wt % Example 3 12 1.60 151 95 wt %
Comparative 9 0.67 1130 66 wt % Example 1 Comparative 13 5.25 236
93 wt % Example 2 Comparative 14 10.00 424 87 wt % Example 3
Comparative 8 0.55 1570 52 wt % Example 6 Comparative 7 0.39 1760
47 wt % Example 7
[0096] As shown in Table 1 and FIG. 3, in Examples 1 to 3, in which
the pH was adjusted to 10 to 12 through sodium hydroxide in step 2,
the lithium content of lithium phosphate produced were all 94 wt %
or more with respect to the waste solution lithium, and Example 1
with the pH adjusted to 11 was found to show the best lithium
recovery rate. On the other hand, Comparative Example 1 in which
the pH was adjusted to 9 showed a lower value, and Comparative
Examples 2 and 3 in which the pH was adjusted to 13 and 13.5 were
lower in recovery rate than in Example 1, and sodium hydroxide was
used excessively in an amount of 5.about.10 times more than that of
Example 1, thereby causing the process cost to increase and
resulting in an adverse effect of increase in wastewater treatment
costs. The reason why the recovery rates of Comparative Examples 2
and 3 are lowered is because, as described above, a part of lithium
is produced as lithium hydroxide due to the excessive amount of
sodium hydroxide added, and lithium is dissolved again due to
solubility of lithium hydroxide, resulting in an increase in
lithium concentration in the lithium recovered filtrate.
<Experimental Example 2> Comparison of Lithium Recovery
According to Raised Temperature
[0097] The lithium contents of the lithium phosphate produced in
Examples 1, 4 and 5 and Comparative Examples 4, 5, 8 and 9 were
compared based on the lithium content of a waste solution and the
results are shown in Tables 2 and 4 below.
TABLE-US-00002 TABLE 2 Lithium content Raised Concentration of of
lithium phosphate temperature of filtrate after Li with respect to
step 3 (.degree. C.) recovery (ppm) waste solution lithium Example
1 80 169 95 wt % Example 4 70 223 93 wt % Example 5 90 160 95 wt %
Comparative 50 771 77 wt % Example 4 Comparative 100 171 95 wt %
Example 5 Comparative 60 426 87 wt % Example 8 Comparative 25 1670
49 wt % Example 6
[0098] As shown in Table 2 and FIG. 4, in Examples 1, 4 and 5 in
which the raised temperature in step 3 was adjusted to 70 to
90.degree. C., it was shown that the lithium content of lithium
phosphate produced were all 93 wt % or more with respect to waste
solution lithium, and Comparative Example 5 at 100.degree. C. shows
a similar recovery rate as that of Example 1, but shows a poor
result in terms of efficiency relative to the energy cost for
raising the temperature. In Comparative Example 4, in which the
temperature was raised to 50.degree. C., it was confirmed that the
lithium recovery rate was lowered, and this seems to be due to the
solubility of lithium phosphate being inversely proportional with
temperature wherein the solubility becomes lower as the temperature
is higher and becomes higher as the temperature is lower.
[0099] Although a specific embodiment of the lithium phosphate
producing method has been described above, it is apparent that
various modifications can be made without departing from the scope
of the present invention.
[0100] Therefore, the scope of the present invention should not be
construed as being limited to the embodiments described, but should
be determined by equivalents to the appended claims, as well as the
following claims.
[0101] That is, it is to be understood that the foregoing
embodiments are illustrative and not restrictive in all aspects and
that the scope of the present invention is indicated by the
appended claims rather than the foregoing description, and it is
intended that all changes and modifications derived from the
equivalent concept be included within the scope of the present
invention.
* * * * *